BOOK VALUE, the monetary value of an asset as shown in the books of account (q.v.). The book value is calculated by deducting from the cost price as shown on the books the depre ciation which has been set up against it. Thus the book value of a machine which cost $1,5oo and which has been depreciated $3oo would be $1,2oo. An appraised value might be higher or lower than the book value. The book value of a share of common stock in a company having no preferred issues is determined by dividing the excess of assets over liabilities by the number of shares outstanding. The market value of the share as indicated by quotations on a securities exchange might be higher or lower than the book value of the share. Generally speaking, there need not be any close coincidence between the book value and the appraised value or the market value. (See VALUE.) the name given to various insects, moths, beetles, etc., whose larval (or adult) forms injure books by gnaw ing the binding and piercing the leaves with small holes. There is, however, no insect which may properly be called the book-worm, for many of the numerous insects that feed upon dry, starchy material may cause damage to books. Among the most widely known of these are, the bread beetle and the spider beetle, both belonging to the death-watch family (Ptinidae).